1. Technical Field
The invention relates to protecting sensitive facilities by tracking the movement of objects and persons within such facilities. More particularly, the invention relates to zone determination by combining signal strength with topological factors.
2. Description of the Prior Art
Advanced security within facilities was, until recently, was restricted to highly sensitive establishments such as embassies, banks and intelligence groups. The vast majority of facilities simply had perimeter control, with security staff controlling who could enter a building, but once inside people could (with a little tenacity) access almost any area.
Over the past 20 years, with an increased awareness of intellectual and asset theft, many facilities introduced access control badges to restrict access within a facility. But these basic security technologies are easily by-passed. An intruder, for example, can use a stolen (or borrowed) employee badge; contractors (such as janitorial staff) often have facility wide clearance, and intruders frequently simply ask an employee to let them into a restricted area.
With growing incidents of terrorism, pervasive intelligence and company secrets theft, and fear of VIP abduction, forward thinking companies have begun to introduce internal biometrics and other technologies to manage and control access to areas or zones within a facility. But these technologies quickly begin to affect productivity and morale.
Once again the security organization faces the tradeoff between securing a facility, while allowing operations to proceed virtually unhindered.
In view of the continuing risk to property and human life attendant with today's industrial espionage, terrorism and theft, it would be advantageous to provide techniques for minimizing threats and risks within at-risk facilities while allowing normal operations to proceed with minimal disruption. One way to do this is to track the movement of objects and persons within such facilities. For example, active RFID technologies are often used to tag assets and people within buildings or open areas, such as parking lots or military bases. Most real time location systems (RTLS) use a mesh of multiple readers, typically a minimum of three readers, to triangulate the location of the tracked object, e.g. an object bearing an RFID tag. These systems rely on the fact that the tag signal strength diminishes with distance. The signal strength of the tag transmission is then determined from multiple locations. The location of the tag is computed by estimating the distance from multiple readers and, thereafter, estimating the probable location of the object.
Some RFID technologies, however, do not exhibit a smooth reduction in signal strength over distance, making the RTLS computations spurious. It would be advantageous to provide a more reliable way to track objects and persons within critical facilities; that is, more accurately determine the zone of objects and persons in near real-time.